1. Field
Advancements in image decoding are needed to provide improvements in one or more of performance, power utilization, cost, scalability, efficiency, and utility of use.
2. Related Art
Unless expressly identified as being publicly or well known, mention herein of techniques and concepts, including for context, definitions, or comparison purposes, should not be construed as an admission that such techniques and concepts are previously publicly known or otherwise part of the prior art. All references cited herein (if any), including patents, patent applications, and publications, are hereby incorporated by reference in their entireties, whether specifically incorporated or not, for all purposes.
An image processing system includes an image encoder to encode an image to be transmitted and/or stored, and an image decoder to decode the image after reception of a transmission and/or retrieval from storage. The image decoder stores the decoded image, such as in a frame buffer, in a format compatible with a display device. The frame buffer is repeatedly read to refresh the display device. In some image processing systems, a stream of images is encoded and transmitted (or stored), and the image decoder repeatedly updates the frame buffer as the encoded stream of images is decoded so that the display device displays the stream of decoded images. In further image processing systems, such as MPEG systems, some images of the stream of images are sent in a residually encoded format as a difference from a previous image, rather than as a separate image.
Some image encoders, such as JPEG2000 encoders, use a progressive image encoding where an image in a spatial domain is transformed to a frequency domain, such as by a Discrete Cosign Transform (DCT), and then is provided to an image decoder as a series of progressively encoded image updates, each update providing more resolution (for example, higher frequencies in the frequency domain), than the previous. A progressive image decoder is enabled to receive the progress image updates, to quickly display a rough version of the image based on early ones of the progressively encoded image updates, and to build up and display more accurate versions of the image as further ones of the progressively encoded image updates are received. To receive and to process the progressively encoded image updates, some progressive image decoders store both a frequency-encoded version of the image to which the progressively encoded image updates are applied, and a spatially-encoded version of the image in a frame buffer for output to a display device.